compiler/rustc_symbol_mangling/src/v0.rs

   1 use rustc_data_structures::base_n;
   2 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
   3 use rustc_data_structures::intern::Interned;
   4 use rustc_hir as hir;
   5 use rustc_hir::def::CtorKind;
   6 use rustc_hir::def_id::{CrateNum, DefId};
   7 use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
   8 use rustc_middle::ty::layout::IntegerExt;
   9 use rustc_middle::ty::print::{Print, Printer};
  10 use rustc_middle::ty::{
  11     self, EarlyBinder, FloatTy, Instance, IntTy, Ty, TyCtxt, TypeVisitable, UintTy,
  12 };
  13 use rustc_middle::ty::{GenericArg, GenericArgKind};
  14 use rustc_span::symbol::kw;
  15 use rustc_target::abi::Integer;
  16 use rustc_target::spec::abi::Abi;
  17
  18 use std::fmt::Write;
  19 use std::iter;
  20 use std::ops::Range;
  21
  22 pub(super) fn mangle<'tcx>(
  23     tcx: TyCtxt<'tcx>,
  24     instance: Instance<'tcx>,
  25     instantiating_crate: Option<CrateNum>,
  26 ) -> String {
  27     let def_id = instance.def_id();
  28     // FIXME(eddyb) this should ideally not be needed.
  29     let substs = tcx.normalize_erasing_regions(ty::ParamEnv::reveal_all(), instance.substs);
  30
  31     let prefix = "_R";
  32     let mut cx = &mut SymbolMangler {
  33         tcx,
  34         start_offset: prefix.len(),
  35         paths: FxHashMap::default(),
  36         types: FxHashMap::default(),
  37         consts: FxHashMap::default(),
  38         binders: vec![],
  39         out: String::from(prefix),
  40     };
  41
  42     // Append `::{shim:...#0}` to shims that can coexist with a non-shim instance.
  43     let shim_kind = match instance.def {
  44         ty::InstanceDef::VTableShim(_) => Some("vtable"),
  45         ty::InstanceDef::ReifyShim(_) => Some("reify"),
  46
  47         _ => None,
  48     };
  49
  50     cx = if let Some(shim_kind) = shim_kind {
  51         cx.path_append_ns(|cx| cx.print_def_path(def_id, substs), 'S', 0, shim_kind).unwrap()
  52     } else {
  53         cx.print_def_path(def_id, substs).unwrap()
  54     };
  55     if let Some(instantiating_crate) = instantiating_crate {
  56         cx = cx.print_def_path(instantiating_crate.as_def_id(), &[]).unwrap();
  57     }
  58     std::mem::take(&mut cx.out)
  59 }
  60
  61 pub(super) fn mangle_typeid_for_trait_ref<'tcx>(
  62     tcx: TyCtxt<'tcx>,
  63     trait_ref: ty::PolyExistentialTraitRef<'tcx>,
  64 ) -> String {
  65     // FIXME(flip1995): See comment in `mangle_typeid_for_fnabi`.
  66     let mut cx = &mut SymbolMangler {
  67         tcx,
  68         start_offset: 0,
  69         paths: FxHashMap::default(),
  70         types: FxHashMap::default(),
  71         consts: FxHashMap::default(),
  72         binders: vec![],
  73         out: String::new(),
  74     };
  75     cx = cx.print_def_path(trait_ref.def_id(), &[]).unwrap();
  76     std::mem::take(&mut cx.out)
  77 }
  78
  79 struct BinderLevel {
  80     /// The range of distances from the root of what's
  81     /// being printed, to the lifetimes in a binder.
  82     /// Specifically, a `BrAnon(i)` lifetime has depth
  83     /// `lifetime_depths.start + i`, going away from the
  84     /// the root and towards its use site, as `i` increases.
  85     /// This is used to flatten rustc's pairing of `BrAnon`
  86     /// (intra-binder disambiguation) with a `DebruijnIndex`
  87     /// (binder addressing), to "true" de Bruijn indices,
  88     /// by subtracting the depth of a certain lifetime, from
  89     /// the innermost depth at its use site.
  90     lifetime_depths: Range<u32>,
  91 }
  92
  93 struct SymbolMangler<'tcx> {
  94     tcx: TyCtxt<'tcx>,
  95     binders: Vec<BinderLevel>,
  96     out: String,
  97
  98     /// The length of the prefix in `out` (e.g. 2 for `_R`).
  99     start_offset: usize,
 100     /// The values are start positions in `out`, in bytes.
 101     paths: FxHashMap<(DefId, &'tcx [GenericArg<'tcx>]), usize>,
 102     types: FxHashMap<Ty<'tcx>, usize>,
 103     consts: FxHashMap<ty::Const<'tcx>, usize>,
 104 }
 105
 106 impl<'tcx> SymbolMangler<'tcx> {
 107     fn push(&mut self, s: &str) {
 108         self.out.push_str(s);
 109     }
 110
 111     /// Push a `_`-terminated base 62 integer, using the format
 112     /// specified in the RFC as `<base-62-number>`, that is:
 113     /// * `x = 0` is encoded as just the `"_"` terminator
 114     /// * `x > 0` is encoded as `x - 1` in base 62, followed by `"_"`,
 115     ///   e.g. `1` becomes `"0_"`, `62` becomes `"Z_"`, etc.
 116     fn push_integer_62(&mut self, x: u64) {
 117         if let Some(x) = x.checked_sub(1) {
 118             base_n::push_str(x as u128, 62, &mut self.out);
 119         }
 120         self.push("_");
 121     }
 122
 123     /// Push a `tag`-prefixed base 62 integer, when larger than `0`, that is:
 124     /// * `x = 0` is encoded as `""` (nothing)
 125     /// * `x > 0` is encoded as the `tag` followed by `push_integer_62(x - 1)`
 126     ///   e.g. `1` becomes `tag + "_"`, `2` becomes `tag + "0_"`, etc.
 127     fn push_opt_integer_62(&mut self, tag: &str, x: u64) {
 128         if let Some(x) = x.checked_sub(1) {
 129             self.push(tag);
 130             self.push_integer_62(x);
 131         }
 132     }
 133
 134     fn push_disambiguator(&mut self, dis: u64) {
 135         self.push_opt_integer_62("s", dis);
 136     }
 137
 138     fn push_ident(&mut self, ident: &str) {
 139         let mut use_punycode = false;
 140         for b in ident.bytes() {
 141             match b {
 142                 b'_' | b'a'..=b'z' | b'A'..=b'Z' | b'0'..=b'9' => {}
 143                 0x80..=0xff => use_punycode = true,
 144                 _ => bug!("symbol_names: bad byte {} in ident {:?}", b, ident),
 145             }
 146         }
 147
 148         let punycode_string;
 149         let ident = if use_punycode {
 150             self.push("u");
 151
 152             // FIXME(eddyb) we should probably roll our own punycode implementation.
 153             let mut punycode_bytes = match punycode::encode(ident) {
 154                 Ok(s) => s.into_bytes(),
 155                 Err(()) => bug!("symbol_names: punycode encoding failed for ident {:?}", ident),
 156             };
 157
 158             // Replace `-` with `_`.
 159             if let Some(c) = punycode_bytes.iter_mut().rfind(|&&mut c| c == b'-') {
 160                 *c = b'_';
 161             }
 162
 163             // FIXME(eddyb) avoid rechecking UTF-8 validity.
 164             punycode_string = String::from_utf8(punycode_bytes).unwrap();
 165             &punycode_string
 166         } else {
 167             ident
 168         };
 169
 170         let _ = write!(self.out, "{}", ident.len());
 171
 172         // Write a separating `_` if necessary (leading digit or `_`).
 173         if let Some('_' | '0'..='9') = ident.chars().next() {
 174             self.push("_");
 175         }
 176
 177         self.push(ident);
 178     }
 179
 180     fn path_append_ns<'a>(
 181         mut self: &'a mut Self,
 182         print_prefix: impl FnOnce(&'a mut Self) -> Result<&'a mut Self, !>,
 183         ns: char,
 184         disambiguator: u64,
 185         name: &str,
 186     ) -> Result<&'a mut Self, !> {
 187         self.push("N");
 188         self.out.push(ns);
 189         self = print_prefix(self)?;
 190         self.push_disambiguator(disambiguator as u64);
 191         self.push_ident(name);
 192         Ok(self)
 193     }
 194
 195     fn print_backref(&mut self, i: usize) -> Result<&mut Self, !> {
 196         self.push("B");
 197         self.push_integer_62((i - self.start_offset) as u64);
 198         Ok(self)
 199     }
 200
 201     fn in_binder<'a, T>(
 202         mut self: &'a mut Self,
 203         value: &ty::Binder<'tcx, T>,
 204         print_value: impl FnOnce(&'a mut Self, &T) -> Result<&'a mut Self, !>,
 205     ) -> Result<&'a mut Self, !>
 206     where
 207         T: TypeVisitable<'tcx>,
 208     {
 209         // FIXME(non-lifetime-binders): What to do here?
 210         let regions = if value.has_late_bound_regions() {
 211             self.tcx.collect_referenced_late_bound_regions(value)
 212         } else {
 213             FxHashSet::default()
 214         };
 215
 216         let mut lifetime_depths =
 217             self.binders.last().map(|b| b.lifetime_depths.end).map_or(0..0, |i| i..i);
 218
 219         let lifetimes = regions
 220             .into_iter()
 221             .map(|br| match br {
 222                 ty::BrAnon(i, _) => i,
 223                 _ => bug!("symbol_names: non-anonymized region `{:?}` in `{:?}`", br, value),
 224             })
 225             .max()
 226             .map_or(0, |max| max + 1);
 227
 228         self.push_opt_integer_62("G", lifetimes as u64);
 229         lifetime_depths.end += lifetimes;
 230
 231         self.binders.push(BinderLevel { lifetime_depths });
 232         self = print_value(self, value.as_ref().skip_binder())?;
 233         self.binders.pop();
 234
 235         Ok(self)
 236     }
 237 }
 238
 239 impl<'tcx> Printer<'tcx> for &mut SymbolMangler<'tcx> {
 240     type Error = !;
 241
 242     type Path = Self;
 243     type Region = Self;
 244     type Type = Self;
 245     type DynExistential = Self;
 246     type Const = Self;
 247
 248     fn tcx(&self) -> TyCtxt<'tcx> {
 249         self.tcx
 250     }
 251
 252     fn print_def_path(
 253         mut self,
 254         def_id: DefId,
 255         substs: &'tcx [GenericArg<'tcx>],
 256     ) -> Result<Self::Path, Self::Error> {
 257         if let Some(&i) = self.paths.get(&(def_id, substs)) {
 258             return self.print_backref(i);
 259         }
 260         let start = self.out.len();
 261
 262         self = self.default_print_def_path(def_id, substs)?;
 263
 264         // Only cache paths that do not refer to an enclosing
 265         // binder (which would change depending on context).
 266         if !substs.iter().any(|k| k.has_escaping_bound_vars()) {
 267             self.paths.insert((def_id, substs), start);
 268         }
 269         Ok(self)
 270     }
 271
 272     fn print_impl_path(
 273         mut self,
 274         impl_def_id: DefId,
 275         substs: &'tcx [GenericArg<'tcx>],
 276         mut self_ty: Ty<'tcx>,
 277         mut impl_trait_ref: Option<ty::TraitRef<'tcx>>,
 278     ) -> Result<Self::Path, Self::Error> {
 279         let key = self.tcx.def_key(impl_def_id);
 280         let parent_def_id = DefId { index: key.parent.unwrap(), ..impl_def_id };
 281
 282         let mut param_env = self.tcx.param_env_reveal_all_normalized(impl_def_id);
 283         if !substs.is_empty() {
 284             param_env = EarlyBinder(param_env).subst(self.tcx, substs);
 285         }
 286
 287         match &mut impl_trait_ref {
 288             Some(impl_trait_ref) => {
 289                 assert_eq!(impl_trait_ref.self_ty(), self_ty);
 290                 *impl_trait_ref = self.tcx.normalize_erasing_regions(param_env, *impl_trait_ref);
 291                 self_ty = impl_trait_ref.self_ty();
 292             }
 293             None => {
 294                 self_ty = self.tcx.normalize_erasing_regions(param_env, self_ty);
 295             }
 296         }
 297
 298         self.push(match impl_trait_ref {
 299             Some(_) => "X",
 300             None => "M",
 301         });
 302
 303         // Encode impl generic params if the substitutions contain parameters (implying
 304         // polymorphization is enabled) and this isn't an inherent impl.
 305         if impl_trait_ref.is_some() && substs.iter().any(|a| a.has_non_region_param()) {
 306             self = self.path_generic_args(
 307                 |this| {
 308                     this.path_append_ns(
 309                         |cx| cx.print_def_path(parent_def_id, &[]),
 310                         'I',
 311                         key.disambiguated_data.disambiguator as u64,
 312                         "",
 313                     )
 314                 },
 315                 substs,
 316             )?;
 317         } else {
 318             self.push_disambiguator(key.disambiguated_data.disambiguator as u64);
 319             self = self.print_def_path(parent_def_id, &[])?;
 320         }
 321
 322         self = self_ty.print(self)?;
 323
 324         if let Some(trait_ref) = impl_trait_ref {
 325             self = self.print_def_path(trait_ref.def_id, trait_ref.substs)?;
 326         }
 327
 328         Ok(self)
 329     }
 330
 331     fn print_region(self, region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
 332         let i = match *region {
 333             // Erased lifetimes use the index 0, for a
 334             // shorter mangling of `L_`.
 335             ty::ReErased => 0,
 336
 337             // Late-bound lifetimes use indices starting at 1,
 338             // see `BinderLevel` for more details.
 339             ty::ReLateBound(debruijn, ty::BoundRegion { kind: ty::BrAnon(i, _), .. }) => {
 340                 let binder = &self.binders[self.binders.len() - 1 - debruijn.index()];
 341                 let depth = binder.lifetime_depths.start + i;
 342
 343                 1 + (self.binders.last().unwrap().lifetime_depths.end - 1 - depth)
 344             }
 345
 346             _ => bug!("symbol_names: non-erased region `{:?}`", region),
 347         };
 348         self.push("L");
 349         self.push_integer_62(i as u64);
 350         Ok(self)
 351     }
 352
 353     fn print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
 354         // Basic types, never cached (single-character).
 355         let basic_type = match ty.kind() {
 356             ty::Bool => "b",
 357             ty::Char => "c",
 358             ty::Str => "e",
 359             ty::Tuple(_) if ty.is_unit() => "u",
 360             ty::Int(IntTy::I8) => "a",
 361             ty::Int(IntTy::I16) => "s",
 362             ty::Int(IntTy::I32) => "l",
 363             ty::Int(IntTy::I64) => "x",
 364             ty::Int(IntTy::I128) => "n",
 365             ty::Int(IntTy::Isize) => "i",
 366             ty::Uint(UintTy::U8) => "h",
 367             ty::Uint(UintTy::U16) => "t",
 368             ty::Uint(UintTy::U32) => "m",
 369             ty::Uint(UintTy::U64) => "y",
 370             ty::Uint(UintTy::U128) => "o",
 371             ty::Uint(UintTy::Usize) => "j",
 372             ty::Float(FloatTy::F32) => "f",
 373             ty::Float(FloatTy::F64) => "d",
 374             ty::Never => "z",
 375
 376             // Placeholders (should be demangled as `_`).
 377             ty::Param(_) | ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => "p",
 378
 379             _ => "",
 380         };
 381         if !basic_type.is_empty() {
 382             self.push(basic_type);
 383             return Ok(self);
 384         }
 385
 386         if let Some(&i) = self.types.get(&ty) {
 387             return self.print_backref(i);
 388         }
 389         let start = self.out.len();
 390
 391         match *ty.kind() {
 392             // Basic types, handled above.
 393             ty::Bool | ty::Char | ty::Str | ty::Int(_) | ty::Uint(_) | ty::Float(_) | ty::Never => {
 394                 unreachable!()
 395             }
 396             ty::Tuple(_) if ty.is_unit() => unreachable!(),
 397
 398             // Placeholders, also handled as part of basic types.
 399             ty::Param(_) | ty::Bound(..) | ty::Placeholder(_) | ty::Infer(_) | ty::Error(_) => {
 400                 unreachable!()
 401             }
 402
 403             ty::Ref(r, ty, mutbl) => {
 404                 self.push(match mutbl {
 405                     hir::Mutability::Not => "R",
 406                     hir::Mutability::Mut => "Q",
 407                 });
 408                 if !r.is_erased() {
 409                     self = r.print(self)?;
 410                 }
 411                 self = ty.print(self)?;
 412             }
 413
 414             ty::RawPtr(mt) => {
 415                 self.push(match mt.mutbl {
 416                     hir::Mutability::Not => "P",
 417                     hir::Mutability::Mut => "O",
 418                 });
 419                 self = mt.ty.print(self)?;
 420             }
 421
 422             ty::Array(ty, len) => {
 423                 self.push("A");
 424                 self = ty.print(self)?;
 425                 self = self.print_const(len)?;
 426             }
 427             ty::Slice(ty) => {
 428                 self.push("S");
 429                 self = ty.print(self)?;
 430             }
 431
 432             ty::Tuple(tys) => {
 433                 self.push("T");
 434                 for ty in tys.iter() {
 435                     self = ty.print(self)?;
 436                 }
 437                 self.push("E");
 438             }
 439
 440             // Mangle all nominal types as paths.
 441             ty::Adt(ty::AdtDef(Interned(&ty::AdtDefData { did: def_id, .. }, _)), substs)
 442             | ty::FnDef(def_id, substs)
 443             | ty::Alias(_, ty::AliasTy { def_id, substs, .. })
 444             | ty::Closure(def_id, substs)
 445             | ty::Generator(def_id, substs, _) => {
 446                 self = self.print_def_path(def_id, substs)?;
 447             }
 448             ty::Foreign(def_id) => {
 449                 self = self.print_def_path(def_id, &[])?;
 450             }
 451
 452             ty::FnPtr(sig) => {
 453                 self.push("F");
 454                 self = self.in_binder(&sig, |mut cx, sig| {
 455                     if sig.unsafety == hir::Unsafety::Unsafe {
 456                         cx.push("U");
 457                     }
 458                     match sig.abi {
 459                         Abi::Rust => {}
 460                         Abi::C { unwind: false } => cx.push("KC"),
 461                         abi => {
 462                             cx.push("K");
 463                             let name = abi.name();
 464                             if name.contains('-') {
 465                                 cx.push_ident(&name.replace('-', "_"));
 466                             } else {
 467                                 cx.push_ident(name);
 468                             }
 469                         }
 470                     }
 471                     for &ty in sig.inputs() {
 472                         cx = ty.print(cx)?;
 473                     }
 474                     if sig.c_variadic {
 475                         cx.push("v");
 476                     }
 477                     cx.push("E");
 478                     sig.output().print(cx)
 479                 })?;
 480             }
 481
 482             ty::Dynamic(predicates, r, kind) => {
 483                 self.push(match kind {
 484                     ty::Dyn => "D",
 485                     // FIXME(dyn-star): need to update v0 mangling docs
 486                     ty::DynStar => "D*",
 487                 });
 488                 self = self.print_dyn_existential(predicates)?;
 489                 self = r.print(self)?;
 490             }
 491
 492             ty::GeneratorWitness(_) => bug!("symbol_names: unexpected `GeneratorWitness`"),
 493         }
 494
 495         // Only cache types that do not refer to an enclosing
 496         // binder (which would change depending on context).
 497         if !ty.has_escaping_bound_vars() {
 498             self.types.insert(ty, start);
 499         }
 500         Ok(self)
 501     }
 502
 503     fn print_dyn_existential(
 504         mut self,
 505         predicates: &'tcx ty::List<ty::PolyExistentialPredicate<'tcx>>,
 506     ) -> Result<Self::DynExistential, Self::Error> {
 507         // Okay, so this is a bit tricky. Imagine we have a trait object like
 508         // `dyn for<'a> Foo<'a, Bar = &'a ()>`. When we mangle this, the
 509         // output looks really close to the syntax, where the `Bar = &'a ()` bit
 510         // is under the same binders (`['a]`) as the `Foo<'a>` bit. However, we
 511         // actually desugar these into two separate `ExistentialPredicate`s. We
 512         // can't enter/exit the "binder scope" twice though, because then we
 513         // would mangle the binders twice. (Also, side note, we merging these
 514         // two is kind of difficult, because of potential HRTBs in the Projection
 515         // predicate.)
 516         //
 517         // Also worth mentioning: imagine that we instead had
 518         // `dyn for<'a> Foo<'a, Bar = &'a ()> + Send`. In this case, `Send` is
 519         // under the same binders as `Foo`. Currently, this doesn't matter,
 520         // because only *auto traits* are allowed other than the principal trait
 521         // and all auto traits don't have any generics. Two things could
 522         // make this not an "okay" mangling:
 523         // 1) Instead of mangling only *used*
 524         // bound vars, we want to mangle *all* bound vars (`for<'b> Send` is a
 525         // valid trait predicate);
 526         // 2) We allow multiple "principal" traits in the future, or at least
 527         // allow in any form another trait predicate that can take generics.
 528         //
 529         // Here we assume that predicates have the following structure:
 530         // [<Trait> [{<Projection>}]] [{<Auto>}]
 531         // Since any predicates after the first one shouldn't change the binders,
 532         // just put them all in the binders of the first.
 533         self = self.in_binder(&predicates[0], |mut cx, _| {
 534             for predicate in predicates.iter() {
 535                 // It would be nice to be able to validate bound vars here, but
 536                 // projections can actually include bound vars from super traits
 537                 // because of HRTBs (only in the `Self` type). Also, auto traits
 538                 // could have different bound vars *anyways*.
 539                 match predicate.as_ref().skip_binder() {
 540                     ty::ExistentialPredicate::Trait(trait_ref) => {
 541                         // Use a type that can't appear in defaults of type parameters.
 542                         let dummy_self = cx.tcx.mk_ty_infer(ty::FreshTy(0));
 543                         let trait_ref = trait_ref.with_self_ty(cx.tcx, dummy_self);
 544                         cx = cx.print_def_path(trait_ref.def_id, trait_ref.substs)?;
 545                     }
 546                     ty::ExistentialPredicate::Projection(projection) => {
 547                         let name = cx.tcx.associated_item(projection.def_id).name;
 548                         cx.push("p");
 549                         cx.push_ident(name.as_str());
 550                         cx = match projection.term.unpack() {
 551                             ty::TermKind::Ty(ty) => ty.print(cx),
 552                             ty::TermKind::Const(c) => c.print(cx),
 553                         }?;
 554                     }
 555                     ty::ExistentialPredicate::AutoTrait(def_id) => {
 556                         cx = cx.print_def_path(*def_id, &[])?;
 557                     }
 558                 }
 559             }
 560             Ok(cx)
 561         })?;
 562
 563         self.push("E");
 564         Ok(self)
 565     }
 566
 567     fn print_const(mut self, ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
 568         // We only mangle a typed value if the const can be evaluated.
 569         let ct = ct.eval(self.tcx, ty::ParamEnv::reveal_all());
 570         match ct.kind() {
 571             ty::ConstKind::Value(_) => {}
 572
 573             // Placeholders (should be demangled as `_`).
 574             // NOTE(eddyb) despite `Unevaluated` having a `DefId` (and therefore
 575             // a path), even for it we still need to encode a placeholder, as
 576             // the path could refer back to e.g. an `impl` using the constant.
 577             ty::ConstKind::Unevaluated(_)
 578             | ty::ConstKind::Expr(_)
 579             | ty::ConstKind::Param(_)
 580             | ty::ConstKind::Infer(_)
 581             | ty::ConstKind::Bound(..)
 582             | ty::ConstKind::Placeholder(_)
 583             | ty::ConstKind::Error(_) => {
 584                 // Never cached (single-character).
 585                 self.push("p");
 586                 return Ok(self);
 587             }
 588         }
 589
 590         if let Some(&i) = self.consts.get(&ct) {
 591             return self.print_backref(i);
 592         }
 593
 594         let start = self.out.len();
 595         let ty = ct.ty();
 596
 597         match ty.kind() {
 598             ty::Uint(_) | ty::Int(_) | ty::Bool | ty::Char => {
 599                 self = ty.print(self)?;
 600
 601                 let mut bits = ct.eval_bits(self.tcx, ty::ParamEnv::reveal_all(), ty);
 602
 603                 // Negative integer values are mangled using `n` as a "sign prefix".
 604                 if let ty::Int(ity) = ty.kind() {
 605                     let val =
 606                         Integer::from_int_ty(&self.tcx, *ity).size().sign_extend(bits) as i128;
 607                     if val < 0 {
 608                         self.push("n");
 609                     }
 610                     bits = val.unsigned_abs();
 611                 }
 612
 613                 let _ = write!(self.out, "{bits:x}_");
 614             }
 615
 616             // FIXME(valtrees): Remove the special case for `str`
 617             // here and fully support unsized constants.
 618             ty::Ref(_, inner_ty, mutbl) => {
 619                 self.push(match mutbl {
 620                     hir::Mutability::Not => "R",
 621                     hir::Mutability::Mut => "Q",
 622                 });
 623
 624                 match inner_ty.kind() {
 625                     ty::Str if mutbl.is_not() => {
 626                         match ct.kind() {
 627                             ty::ConstKind::Value(valtree) => {
 628                                 let slice =
 629                                     valtree.try_to_raw_bytes(self.tcx(), ty).unwrap_or_else(|| {
 630                                         bug!(
 631                                         "expected to get raw bytes from valtree {:?} for type {:}",
 632                                         valtree, ty
 633                                     )
 634                                     });
 635                                 let s = std::str::from_utf8(slice).expect("non utf8 str from miri");
 636
 637                                 self.push("e");
 638
 639                                 // FIXME(eddyb) use a specialized hex-encoding loop.
 640                                 for byte in s.bytes() {
 641                                     let _ = write!(self.out, "{byte:02x}");
 642                                 }
 643
 644                                 self.push("_");
 645                             }
 646
 647                             _ => {
 648                                 bug!("symbol_names: unsupported `&str` constant: {:?}", ct);
 649                             }
 650                         }
 651                     }
 652                     _ => {
 653                         let pointee_ty = ct
 654                             .ty()
 655                             .builtin_deref(true)
 656                             .expect("tried to dereference on non-ptr type")
 657                             .ty;
 658                         let dereferenced_const = self.tcx.mk_const(ct.kind(), pointee_ty);
 659                         self = dereferenced_const.print(self)?;
 660                     }
 661                 }
 662             }
 663
 664             ty::Array(..) | ty::Tuple(..) | ty::Adt(..) | ty::Slice(_) => {
 665                 let contents = self.tcx.destructure_const(ct);
 666                 let fields = contents.fields.iter().copied();
 667
 668                 let print_field_list = |mut this: Self| {
 669                     for field in fields.clone() {
 670                         this = field.print(this)?;
 671                     }
 672                     this.push("E");
 673                     Ok(this)
 674                 };
 675
 676                 match *ct.ty().kind() {
 677                     ty::Array(..) | ty::Slice(_) => {
 678                         self.push("A");
 679                         self = print_field_list(self)?;
 680                     }
 681                     ty::Tuple(..) => {
 682                         self.push("T");
 683                         self = print_field_list(self)?;
 684                     }
 685                     ty::Adt(def, substs) => {
 686                         let variant_idx =
 687                             contents.variant.expect("destructed const of adt without variant idx");
 688                         let variant_def = &def.variant(variant_idx);
 689
 690                         self.push("V");
 691                         self = self.print_def_path(variant_def.def_id, substs)?;
 692
 693                         match variant_def.ctor_kind() {
 694                             Some(CtorKind::Const) => {
 695                                 self.push("U");
 696                             }
 697                             Some(CtorKind::Fn) => {
 698                                 self.push("T");
 699                                 self = print_field_list(self)?;
 700                             }
 701                             None => {
 702                                 self.push("S");
 703                                 for (field_def, field) in iter::zip(&variant_def.fields, fields) {
 704                                     // HACK(eddyb) this mimics `path_append`,
 705                                     // instead of simply using `field_def.ident`,
 706                                     // just to be able to handle disambiguators.
 707                                     let disambiguated_field =
 708                                         self.tcx.def_key(field_def.did).disambiguated_data;
 709                                     let field_name = disambiguated_field.data.get_opt_name();
 710                                     self.push_disambiguator(
 711                                         disambiguated_field.disambiguator as u64,
 712                                     );
 713                                     self.push_ident(field_name.unwrap_or(kw::Empty).as_str());
 714
 715                                     self = field.print(self)?;
 716                                 }
 717                                 self.push("E");
 718                             }
 719                         }
 720                     }
 721                     _ => unreachable!(),
 722                 }
 723             }
 724             _ => {
 725                 bug!("symbol_names: unsupported constant of type `{}` ({:?})", ct.ty(), ct);
 726             }
 727         }
 728
 729         // Only cache consts that do not refer to an enclosing
 730         // binder (which would change depending on context).
 731         if !ct.has_escaping_bound_vars() {
 732             self.consts.insert(ct, start);
 733         }
 734         Ok(self)
 735     }
 736
 737     fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
 738         self.push("C");
 739         let stable_crate_id = self.tcx.def_path_hash(cnum.as_def_id()).stable_crate_id();
 740         self.push_disambiguator(stable_crate_id.to_u64());
 741         let name = self.tcx.crate_name(cnum);
 742         self.push_ident(name.as_str());
 743         Ok(self)
 744     }
 745
 746     fn path_qualified(
 747         mut self,
 748         self_ty: Ty<'tcx>,
 749         trait_ref: Option<ty::TraitRef<'tcx>>,
 750     ) -> Result<Self::Path, Self::Error> {
 751         assert!(trait_ref.is_some());
 752         let trait_ref = trait_ref.unwrap();
 753
 754         self.push("Y");
 755         self = self_ty.print(self)?;
 756         self.print_def_path(trait_ref.def_id, trait_ref.substs)
 757     }
 758
 759     fn path_append_impl(
 760         self,
 761         _: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 762         _: &DisambiguatedDefPathData,
 763         _: Ty<'tcx>,
 764         _: Option<ty::TraitRef<'tcx>>,
 765     ) -> Result<Self::Path, Self::Error> {
 766         // Inlined into `print_impl_path`
 767         unreachable!()
 768     }
 769
 770     fn path_append(
 771         self,
 772         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 773         disambiguated_data: &DisambiguatedDefPathData,
 774     ) -> Result<Self::Path, Self::Error> {
 775         let ns = match disambiguated_data.data {
 776             // Extern block segments can be skipped, names from extern blocks
 777             // are effectively living in their parent modules.
 778             DefPathData::ForeignMod => return print_prefix(self),
 779
 780             // Uppercase categories are more stable than lowercase ones.
 781             DefPathData::TypeNs(_) => 't',
 782             DefPathData::ValueNs(_) => 'v',
 783             DefPathData::ClosureExpr => 'C',
 784             DefPathData::Ctor => 'c',
 785             DefPathData::AnonConst => 'k',
 786             DefPathData::ImplTrait => 'i',
 787
 788             // These should never show up as `path_append` arguments.
 789             DefPathData::CrateRoot
 790             | DefPathData::Use
 791             | DefPathData::GlobalAsm
 792             | DefPathData::Impl
 793             | DefPathData::MacroNs(_)
 794             | DefPathData::LifetimeNs(_) => {
 795                 bug!("symbol_names: unexpected DefPathData: {:?}", disambiguated_data.data)
 796             }
 797         };
 798
 799         let name = disambiguated_data.data.get_opt_name();
 800
 801         self.path_append_ns(
 802             print_prefix,
 803             ns,
 804             disambiguated_data.disambiguator as u64,
 805             name.unwrap_or(kw::Empty).as_str(),
 806         )
 807     }
 808
 809     fn path_generic_args(
 810         mut self,
 811         print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
 812         args: &[GenericArg<'tcx>],
 813     ) -> Result<Self::Path, Self::Error> {
 814         // Don't print any regions if they're all erased.
 815         let print_regions = args.iter().any(|arg| match arg.unpack() {
 816             GenericArgKind::Lifetime(r) => !r.is_erased(),
 817             _ => false,
 818         });
 819         let args = args.iter().cloned().filter(|arg| match arg.unpack() {
 820             GenericArgKind::Lifetime(_) => print_regions,
 821             _ => true,
 822         });
 823
 824         if args.clone().next().is_none() {
 825             return print_prefix(self);
 826         }
 827
 828         self.push("I");
 829         self = print_prefix(self)?;
 830         for arg in args {
 831             match arg.unpack() {
 832                 GenericArgKind::Lifetime(lt) => {
 833                     self = lt.print(self)?;
 834                 }
 835                 GenericArgKind::Type(ty) => {
 836                     self = ty.print(self)?;
 837                 }
 838                 GenericArgKind::Const(c) => {
 839                     self.push("K");
 840                     self = c.print(self)?;
 841                 }
 842             }
 843         }
 844         self.push("E");
 845
 846         Ok(self)
 847     }
 848 }